A music hook, also known as a riff, bridge, or introduction, is a musical piece, also usually a simple, short line, passage, or phrase, which is used to "grab the listener" and to make a tune attractive. In music theory, the phrase we are talking about is called a "hook" (also called a "hookline") - it's a chance for a melody or a phrase to come into the music. Since most songs don't have all that many hooks, sometimes it is necessary to add one at the beginning of a song.
A music hook can be a phrase (iterated), a line (dotted line), a selection (synthesis pattern), or a combination of both. It is a small addition to the music and most importantly, it must be well placed in the song. It doesn't have to be a very long one, just a very striking one. To make sure you have found your hook, listen back to every song you have written and try to pinpoint the exact moment when you came up with your hook.
A music book also makes a song more memorable
to listeners, because there is something inherently appealing about music hooks. This is why the chorus is the part of the song that hooks listeners. The chorus is another word for a lyrical line, or a repetitive section of a song. A good chorus will make the listener to remember the lyrics to a tune because they are so catchy.